Uber is suing London's transport authority over plans to test whether drivers' English is good enough.

The ride-hailing company is unhappy with new plans by Transport for London (TFL) that will require private hire drivers from non-English-speaking countries to prove they have passed a written exam testing their English language skills.

The exam costs £200 ($260), which Uber says could force thousands of drivers out of work. The San Francisco-based company is also unhappy about new rules for driver insurance and about TFL's decision that Uber to show regulators new features in the app before launching them to the public.

"This legal action is very much a last resort," Uber's general manager for London, Tom Elvidge, said in a statement Wednesday. "We're particularly disappointed that, after a lengthy consultation process with Transport for London, the goalposts have moved at the last minute."